The present invention relates to a brake lever for attachment to a splined S-cam shaft of an automotive drum brake and connection to a brake cylinder push rod, including
a worm wheel, rotatably mounted in a housing of the brake lever and having internal splines for cooperation with the S-cam shaft, and a worm screw, rotatable in the housing perpendicularly to the worm wheel and meshing therewith, and
a control arrangement for transmitting a control movement from a reference point to a clutch wheel, which is rotatable on the worm screw, depending on the angular movement of the brake lever, and which forms a clutch with the worm screw normally held engaged by a strong compression spring,
the control arrangement including a control disc, which is rotatable coaxially with the worm wheel and is connected to a control ring having a control arm for establishing the reference point by being attached to a fixed part of a vehicle chassis, a pinion meshing with the toothed periphery of the control disc and an adjustment screw, which is coaxial with the pinion and is in tooth engagement with the clutch wheel, wherein the axis of the worm screw is perpendicular to the axis of the pinion and the adjuster screw.
A brake lever or slack adjuster of the kind defined above is disclosed in EP-A-598 290. This brake lever has proven its advantages in practical service and is commercially available.
However, in its control arrangement it contains parts that are somewhat awkward to produce and mount. Also, an adjustment of the desired control distance or A-measure is accomplished by exchange of a part in the control arrangement, which means that several such parts have to be kept in stock. It is further desired to have the possibility to increase the spring bias in the control arrangement for safe-guarding the proper function of the device.
The main object of the invention is thus to alter the control arrangement of the brake lever defined above in such a way that it contains a lower number of parts, which can be produced at lower costs and are easier to mount, even with the possibility for an automated mounting.
This is according to the invention attained in that a cylindrical driver is axially but non-rotatably movable in relation to the pinion coaxial therewith and forms a one-way clutch with a unit including the adjustment screw, which is axially movable a distance corresponding to a desired control distance or A-measure for the brake lever, the one-way clutch being spring-biassed into engagement.
Preferably, the pinion, the driver, and the unit including the adjustment screw are rotatably arranged on a common shaft.
The pinion may be sleeve-shaped for receiving the driver, and a compression spring may be arranged between the pinion and the driver.
The one-way clutch is preferably formed between the driver and a tooth washer connected to the adjustment screw.
The unit of the tooth washer and the adjustment screw is axially movable on the shaft between a shaft shoulder and a counter-nut attached at the end of the shaft. The control distance or A-measure, defined by this axial play, may accordingly easily be set at the factory by moving the counter-nut on the shaft.